Xylitol could be effective as a preventive intervention in helping reduce oral health disparities, especially in Head Start and school-based meal programs. However, it has not been widely adopted and is not included in the caries prevention methods described in recent Surgeon General's Report on Oral Health. The proposed studies about its mechanism of action and the relationship between dose, frequency of use and response, are to address some of the unknowns related to the use of xylitol. In this sense, the work proposed is "non traditional." The proposed research is associated with two other projects in the proposed oral health disparity research center (Pis Roberts and Grossman? and shares methods and pilot data with them. The specific aims of this research are: 1. To determine the relationship between number of exposures and effects on Streptococcus mutons for xylitol gum in young adults. 2. To determine the relationship between dose and effects of S. mutans for xylitol gum with a constant number of exposures in young adults. 3. To compare the bacterial response to new xylitol-containing foods or snacks at an optimal dosage and number of exposures/day to that for xylitol gum in both young adults and children. Four studies are proposed. The first two examine the microbiological effects of frequency and dose of use of xylitolcontaining chewing gum in adult subjects. The third examines the effects of alternative preparations of xylitol in comparison to chewing gum at optimal frequency and dose. The fourth study examines the effects of the alternative preparations of xylitol in children. Subjects for the first 3 adult studies will be 341 adults recruited from among University of Washington students and staff. Study 4 will also require approximately 111 children and will be conducted in preschool or school classrooms in a rural county in SW Washington State.